Water hyacinth: A source of pollution until turned into a solution

Near Baroicha Bazar on the Dhaka-Sylhet highway, Joynal Abedin was emptying the bilge water (water collected at the bottom) from his boat anchored in the Arial Khan River. He was readying the boat to repair the large bamboo structure that holds his fishing net. 

He has another important task too - fix the floating bamboo fence that keeps out the water hyacinth that covers the river. 

This alien plant, considered an aquatic pest, can grow and redistribute vigorously. Its seeds remain viable for around three decades, making it even harder to control it. If allowed, it can clog entire water bodies in no time, especially if the water is stagnant.

Arial Khan River is no exception. As the river lost its flow for different reasons, water hyacinth took over almost the entire length of it, making fishing near to impossible. It also harms the quality of the water necessary for fish population.

"It is an everyday fight to clear the area of water hyacinth. See the bamboo structure that fends off the plants? It cost me Tk6,000 to Tk7,000 to set it up," Joynal Abedin told The Business Standard.

"It also damages the water quality, so, fish cannot thrive," he added.

When grown in huge numbers, the plant can deprive the waterbody of sunlight, rot and deposit on the bed and increase the BOD (biochemical oxygen demand) and COD (chemical oxygen demand) of water in the process, and harm other aquatic plant and fish species.

And fishers like Joynal face it every day of every month of the dry season. During monsoon, however, the plants normally drift to the sea where they die due to salinity. The journey is sometimes impeded by structures like road bridges, Jaynal said.

Then, someone has to release the 'islands' of hyacinth, so it can be carried away by the current. But it is a toilsome work and needs funding and deployment of labour, something fishers can hardly afford.

The plant was brought to British India from Brazil by a tourist in the late 19th century who was amazed by the beauty of its flower. Eventually it took over the waterbodies of the country, including Bengal. Photo: Mumit M

Although Bangladesh is a riverine country, fishery resources captured from inland open sources is only half (28.45%) of 'inland culture' (56.24%). In 2020-21, the total fish production was 46.21 lakh metric ton (mt), 13.01 mt of which came from inland open sources, and 26.39 mt came from closed sources. The rest came from the sea. 

The fisherman from Rajabari village in Raipura Upazila is totally dependent on the river for his livelihood. He used to cultivate crops on leased lands but due to his deteriorating health, he stopped farming.

But fishing does not give him much. His youngest child, a school-going boy, now has to work as a daily labourer to make ends meet.

"I have Tk70,000 to Tk80,000 investment in this, but even covering the expenses is difficult nowadays. I can't even sell it, because there is no buyer," Jaynal said.

"Taking these back to home will also require over Tk1,500. I can neither keep them, nor leave them. The only solution left is to burn them," added an aggrieved Jaynal.

"Is there no solution to the hyacinth problem?" we asked him.

"If it were an acre of space, it could have been cleared. The river is 30 km long, and the whole river is infested with hyacinth. How can the problem be solved!" he replied. 

36 kilometres away on the Rampur Bridge near Bijoynagar in Brahmanbaria, an extraordinary view caught our eyes. The river below was fully covered in blooming water hyacinth. Virtually every inch of it. The flowers looked so beautiful that a car full of foreign tourists stopped and started taking selfies with them.

Sitting on the bridge were two middle-aged local men, staring at the river. After a brief chit-chat, we found out that unlike the tourists, they were not really enjoying the view. The men, Devraj and Narendra from Rampur village, were fishermen. The otherwise beautiful plants just made it impossible to fish in the river. 

There was actually a large net fitted onto a bamboo frame under the bridge, but that would only catch hyacinths and plastic bottles instead of fish. The boat anchored on the ground indicated navigation was also impossible.

Devraj said there are 500 to 700 fishing families in three villages around. None of them can fish in the river in this season.  They are awaiting the monsoon water to wash away the water hyacinth.

Photo: Mumit M

Fortunately, unlike Joynal Abedin from Raipura, Narsingdi, these fishers have farming to do during the lean period. 

"When the river is clear of the plants, I can catch fish worth Tk2,000 to Tk4,000 each day. Now it's zero," said Devraj. 

"The plants will go away when the water level will rise by a metre," the fisherman added.

"Is water hyacinth necessarily bad for fish?" we asked an expert.

"It depends on the depth of the waterbody. If it is too shallow, fish cannot travel. Also, the plant eats up the nutrients from the water, as a result of which the water's natural productivity falls. As it is an alien species, water hyacinth is harmful for native fish species," Dr Md Niamul Naser, professor and chairman of the Department of Zoology at the University of Dhaka told The Business Standard.

The history

Water hyacinth is native to tropical and subtropical South America. It is said that the plant was brought to British India from Brazil by a tourist in the late 19th century who was amazed by the beauty of its flower. The plant has also naturalised in other parts of the world. 

By the 1920s, the plant spread across the country (then Bengal). It hindered navigation and made cultivation of jute and aman paddy hard, posing a threat to the country's economy. The administration found it very difficult to clear the water bodies of the invasive plant. 

In 1936, an act was promulgated to prevent the spread of water hyacinth and to destroy it in Bengal. The Bengal Water Hyacinth Act, 1936 made it illegal 'to grow or cultivate water hyacinth in any garden or in any ornamental water or receptacle.' It was also punishable to keep the plant in any land, premises of water in someone's occupation 'except with a view to destroy it'.

In 1937, the issue of eradicating water hyacinth made it to the political parties' election manifestos. The newly elected Sher-e-Bangla A K Fazlul Huq government paid special attention to implementing this programme. By 1947, the situation got better and many rivers retained navigability. 

Currently, water hyacinth is a problem mainly limited to beels and smaller rivers with little to no water flow. 

The catalysts

During a recent trip in several districts around Dhaka, i.e. Narayanganj, Narsingdi, Kishoreganj and Brahmanbaria, we saw water hyacinth in every river. However, the bigger rivers, the ones that were flowing, such as Shitalkhya, Meghna and Titas, were not clogged by it. On the other hand, the smaller rivers with little water are fully covered by it. 

While the invasive plant takes over very quickly, there are some catalysts that support their growth.

"On the 30 km stretch of Arial Khan River, there are 11 bridges. They have been impeding the journey of the plant towards Meghna. Ten years back, there were fewer of these plants in the river," said Joynal Abedin.

In Sonakhali River in Narayanganj's Araihazar Upazila, it is pollution and encroachment that promoted the growth of the plant. 

Seeing a bamboo net frame in the river, we approached a man who was working nearby. The man - a textile worker named Sohel - told us that there is no fishing activity in the river, not until monsoon comes, because the water was too polluted for any fish to survive.

Photo: Mumit M

Sohel informed us that the river lost its flow after a housing company encroached most of its mouth upstream. As a result, hyacinth took advantage and covered the whole river.

In Rampur in Brahmanbaria, on the other hand, the unnamed branch of Titas River was affected when its confluence with the Titas River was filled by sand traders.  

Other rivers lost their vigour with the course time, due to a number of other reasons, and became an abode of water hyacinth.

The solution lies within

While the plant is rightly considered an aquatic pest, with time, many positive aspects of it were discovered. 

Use of water hyacinth in wastewater treatment has been demonstrated to be highly efficient and inexpensive. One study titled 'Use of Water Hyacinths in Wastewater Treatment' authored by Gian C Gupta, published in the Journal of Environmental Health, has shown that growing water hyacinth in a sewage lagoon system reduces BOD5 up to 95%, TSS (Total suspended solids) up to 90%, nitrogen, phosphorus, heavy metals and pesticide.

Many of Bangladesh's water bodies suffer from overnourishment due to nitrogen and phosphorus brought in through municipal wastewater discharges and agricultural run-off, which causes algal bloom, killing fish population in the process. On the other hand, industrial waste disposal causes heavy metal pollution.

As long as the plant is removed on a regular basis, it can treat our surface water in an inexpensive way where needed.

Water hyacinth has been traditionally used as cattle feed during monsoon when grass becomes scarce due to flooding. It is not a great kind of feed though, as cattle rearers complain that the quality of the milk gets deteriorated if the cow is fed this plant.  It is also used as nutrient-rich fertiliser by farmers. 

But the plant has found new usage in the country in recent years. An organisation in Barisal district's Agailjhara Upazila is manufacturing handmade paper from the plant which people have a bitter-sweet relationship with. Gift items made from that paper are now exported to 25 countries, and thousands of local people are earning from it. The activity is also cleaning the water bodies.

In Kishoreganj, Narsingdi and Joypurhat, many handicraft factories have emerged, which are making products with water hyacinth. The products, which include baskets, placemats, square mats, square boxes etc, are also earning forex.

In Africa, countries greatly affected by water hyacinth invasion in Lake Victoria, have been using the plant to produce biofuel, fertiliser etc, creating employability for a lot of poor people.

More research is underway to turn this source of pollution into a solution.